MEASUREMENT OF SUNSCREEN UVA PROTECTION - AN UNSENSITIZED HUMAN-MODEL

Background: Concerns have recently been raised regarding protection provided by sunscreens in the UVA spectrum. No standard testing protocol exists for quantifying this protection. Objective: These studies were conducted to investigate the components of an ideal test methodology to quantify the UVA protection provided by a sunscreen. Methods: Sunscreen products were tested on unsensitized human subjects with UVA from a xenon are lamp in a protocol similar to the sun protection factor test. The biologic end point was either minimal crythema or tanning 24 hours after UVA exposure. Results: The UVA protection factors ranged from 2.1 to 6.9 depending on the type of absorber and the UVB blocking filter, but not on the irradiance of the source or the type of response (crythema or tanning). Conclusion: This test method provides a realistic in vivo estimate of the amount of UVA protection provided by sunscreens.